In 3GPP (3rd Generation Partnership Project); which is a project aiming to standardize a mobile communication system, the introduction of a Device-to-Device (D2D) proximity service is discussed as a new function on and after Release 12 (see Non Patent Document 1).
The D2D proximity service (D2D ProSe) is a service enabling direct communication without passing through a network within a synchronization cluster including plural synchronized user terminals. The D2D proximity service includes a discovery process (Discovery) in which a proximal terminal is discovered and a communication process (Communication) in which direct communication is performed.